Hybrid inflator with temporary gas generator throttle

Abstract

A dual stage hybrid inflation device includes a first stage gas source including a liquefied gas stored in a first stage pressure vessel and a second stage gas source including a gas generator having a gas output directed into the first stage pressure vessel. The gas generator is isolated from the first stage pressure vessel by a frangible diaphragm that ruptures when the pressure in the gas generator exceeds the pressure in the first stage pressure vessel by a predetermined amount. The gas generator is also isolated from the first stage pressure vessel by an eroding nozzle that temporarily restricts the flow of gas from the gas generator to the first stage pressure vessel after the frangible diaphragm ruptures. The eroding nozzle initially restricts the flow of gas from the gas generator to the first stage pressure vessel to prevent a sudden pressure drop in the gas generator that would cause the pyrotechnic gas generating material to self extinguish. The nozzle then erodes away to allow an unrestricted flow of combustion products from the gas generator to the first stage pressure vessel.

1. An apparatus for inflating an inflatable device comprising:
 a first stage gas source comprising a first stage pressure vessel having an interior volume and a gas exit opening, a pressurized cold gas stored within the interior volume of said first stage pressure vessel, and a remotely actuated valve in fluid communication with said gas exit opening, said remotely actuated valve being responsive to an external signal for opening to provide a gas flow path between said first stage pressure vessel and said inflatable device; 
 a second stage gas source comprising a second stage pressure vessel having an interior volume and a gas output opening directed into said first stage pressure vessel, said second stage gas source further comprising a pyrotechnic gas generating material disposed in the interior volume of said second stage pressure vessel, said pyrotechnic gas generating material being capable of combusting to form a gaseous combustion product; 
 a frangible diaphragm disposed in said gas output opening of said second stage pressure vessel for separating the interior volume of said second stage pressure vessel from the interior volume of said first stage pressure vessel, said frangible diaphragm being rupturable to provide a gas flow path between said second stage pressure vessel and said first stage pressure vessel; and 
 an eroding nozzle disposed in said gas output opening of said second stage pressure vessel, said eroding nozzle providing a flow restriction that decreases in resistance as said gaseous combustion products pass through said eroding nozzle. 
 
   
   
     2. The apparatus of  claim 1 , wherein:
 said eroding nozzle comprises a plate member with an orifice formed therein. 
 
   
   
     3. The apparatus of  claim 1 , further comprising:
 a disc support plate disposed in said gas output opening, said disc support plate having a plurality of non-eroding nozzles in a gas flow path from the interior volume of said second stage pressure vessel to the interior volume of said first stage pressure vessel. 
 
   
   
     4. The apparatus of  claim 1 , wherein:
 said pyrotechnic gas generating material has a critical pressure of at least 1000 psi. 
 
   
   
     5. The apparatus of  claim 1 , wherein:
 said pressurized cold gas comprises a mixture of gases including carbon dioxide and a second gas selected from the group consisting of nitrogen and argon wherein at least a portion of the carbon dioxide is stored in a liquid state. 
 
   
   
     6. The apparatus of  claim 5 , wherein:
 said mixture of gases comprises at least 85% Carbon Dioxide by weight. 
 
   
   
     7. The apparatus of  claim 5 , wherein:
 said mixture of gases comprises at least 90% Carbon Dioxide by weight. 
 
   
   
     8. The apparatus of  claim 5 , wherein:
 said mixture of gases comprises at least 95% Carbon Dioxide by weight. 
 
   
   
     9. The apparatus of  claim 1 , wherein:
 said inflatable device is an inflatable aircraft evacuation slide. 
 
   
   
     10. A method of inflating an inflatable device, comprising:
 providing a first stage gas source comprising a first stage pressure vessel having an interior volume and a gas exit opening, a pressurized cold gas stored within the interior volume of said first stage pressure vessel, and a remotely actuated valve in fluid communication with said gas exit opening, said remotely actuated valve being responsive to an external signal for opening to provide a gas flow path between said first stage pressure vessel and said inflatable device; 
 providing a second stage gas source comprising a second stage pressure vessel having an interior volume and a gas output opening directed into said first stage pressure vessel, the interior volume of said second stage pressure vessel being separated from the interior volume of said first stage pressure vessel by a frangible diaphragm and an eroding nozzle having a predetermined flow area, said second stage gas source further comprising a pyrotechnic gas generating material disposed in the interior volume of said second stage pressure vessel, said pyrotechnic gas generating material being capable of combusting to form a gaseous combustion product; 
 opening said remotely actuated valve to begin a flow of gas from said first stage pressure vessel to said inflatable device; 
 initiating said pyrotechnic gas generating material to cause pressure to increase in said second stage pressure vessel until said frangible diaphragm ruptures and said gaseous combustion product begins to flow through said eroding nozzle into said first stage pressure vessel; and 
 temporarily throttling said flow of gaseous combustion product through said eroding nozzle so as to reduce the rate of pressure drop within said second stage pressure vessel; 
 whereby said pyrotechnic gas generating material does not self extinguish due to a sudden drop in pressure within the interior volume of said second stage pressure vessel. 
 
   
   
     11. The method of  claim 10  further comprising;
 eroding said eroding nozzle to enlarge said predetermined flow area as said gaseous combustion product passes therethrough. 
 
   
   
     12. The method of  claim 11 , wherein:
 said eroding nozzle comprises a plate member with an orifice formed therein. 
 
   
   
     13. A method of inflating an inflatable device, comprising:
 providing a first stage gas source comprising a first stage pressure vessel having an interior volume and a gas exit opening, a pressurized cold gas stored within the interior volume of said first stage pressure vessel, and a remotely actuated valve in fluid communication with said gas exit opening, said remotely actuated valve being responsive to an external signal for opening to provide a gas flow path between said first stage pressure vessel and said inflatable device; 
 providing a second stage gas source comprising a second stage pressure vessel having an interior volume and a gas output opening directed into said first stage pressure vessel, the interior volume of said second stage pressure vessel being separated from the interior volume of said first stage pressure vessel by a frangible diaphragm, said second stage gas source further comprising a pyrotechnic gas generating material disposed in the interior volume of said second stage pressure vessel, said pyrotechnic gas generating material being capable of combusting to form a gaseous combustion product; 
 opening said remotely actuated valve to begin a flow of gas from said first stage pressure vessel to said inflatable device; 
 initiating said pyrotechnic gas generating material to cause pressure to increase in said second stage pressure vessel until said frangible diaphragm ruptures and said gaseous combustion product begins to flow through said gas output opening into said first stage pressure vessel; and 
 temporarily throttling said flow of gaseous combustion product through said gas output opening so as to reduce the rate of pressure drop within said second stage pressure vessel; 
 whereby said pyrotechnic gas generating material does not self extinguish due to a sudden drop in pressure within the interior volume of said second stage pressure vessel.